sparc64: Fix bug in PTRACE_SETFPREGS64 handling.

From: Chris Torek <chris.torek@windriver.com>

>The SPARC64 kernel code for PTRACE_SETFPREGS64 appears to be an exact copy 
>of that for PTRACE_GETFPREGS64.  This means that gdbserver and native 
>64-bit GDB cannot set floating-point registers.

It looks like a simple typo.

Signed-off-by: David S. Miller <davem@davemloft.net>